This proposal seeks to identify a gene causing aortic stenosis (AS), a complex human genetic trait with substantial burden on our nations' cardiovascular health. Epidemiologic studies with high familial recurrence rates and chromosomal anomalies strongly implicate a genetic cause, yet to date, no genes have been identified to cause AS in human. Our approach to disease gene identification is to recruit genetically informative families demonstrating rare Mendelian inheritance to perform linkage analysis and identify the disease gene in the linked interval. This postional cloning approach has been a highly successfully means of disease gene identification, especially in complex traits. Towards this end, we have recruited a four-generation family with 13 members affected with AS that demonstrates autosomal dominant inheritance. Echocardiography confirmed the phenotype assignment in all affected family members. Multipoint linkage analysis using in a 10cM genome wide scan has identified a single 1Mb AS locus that achieves the predicted maximum LOD score of 3.0. All affected individuals are linked and 3 unaffected individuals are linked demonstrating incomplete penetrance. By using a positional cloning approach in this pedigree, we have identified a single AS locus in human. Identification of the AS gene contained in this 1Mb disease-linked interval is the overall purpose in the 3 Specific Aims we propose to 1. Characterize and identify candidate genes in the AS interval, 2. Mutation screen candidate genes in the AS interval; and 3. Evaluate for a gene dose effect in the AS interval. With identification of the AS gene, we will evaluate its overall contribution to the pathogenesis of AS and related disorders and will begin the characterization and functional assessment of this gene during cardiac development. Our linkage result holds the promise of identifying the first gene to cause AS in human and provides the opportunity for novel insights into the disease pathogenesis of this common complex human trait.